Thickness Trends and Sequence Stratigraphy
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Thickness trends and sequence AUTHORS Gary G. Lash Department of Geosciences, stratigraphy of the Middle State University of New York, Fredonia, Fredonia, New York 14063; [email protected] Devonian Marcellus Formation, Gary Lash received his B.S. degree from Kutztown State University (1976) and his M.S. degree Appalachian Basin: and Ph.D. from Lehigh University (1978 and 1980, respectively). He has worked on various as- Implications for Acadian pects of the Middle and Upper Devonian shale successions on western New York. Prior to this work, Lash was involved in stratigraphic and foreland basin evolution structural investigations of thrusted Cambrian– Ordovician deposits of the central Appalachians. Gary G. Lash and Terry Engelder Terry Engelder Department of Geosci- ences, Pennsylvania State University, University Park, Pennsylvania 16802; [email protected] ABSTRACT Terry Engelder, a leading authority on the Mar- Analysis of more than 900 wireline logs indicates that the cellus gas shale play, received his B.S. degree Middle Devonian Marcellus Formation encompasses two third- from the Pennsylvania State University, his M.S. degree from Yale University, and his Ph.D. from order transgressive-regressive (T-R) sequences, MSS1 and MSS2, Texas A&M University. He is currently a professor in ascending order. Compositional elements of the Marcellus of geosciences at Penn State and has previ- Formation crucial to the successful development of this emerg- ously served on the staff of the U.S. Geological ing shale gas play, including quartz, clay, carbonate, pyrite, and Survey, Texaco, and Lamont-Doherty Earth organic carbon, vary predictably within the proposed sequence- Observatory. He has written 150 research ar- stratigraphic framework. Thickness trends of Marcellus T-R ticles, many focused on Appalachia, and a book, Stress Regimes in the Lithosphere. sequences and lithostratigraphic units reflect the interplay of Acadian thrust-load-induced subsidence, short-term base-level fluctuations, and recurrent basement structures. Rapid thick- ACKNOWLEDGEMENTS ening of both T-R sequences, especially MSS2, toward the We thank AAPG reviewers Ashton Embry, northeastern region of the basin preserves a record of greater Berry Tew, Charles Boyer II, Ursula Hammes, accommodation space and proximity to clastic sources early and Karen Glaser for their efforts to improve in the Acadian orogeny. However, local variations in T-R se- this paper. Chief Oil and Gas, LLC, the New York quence thickness in the western, more distal, area of the basin State Energy Research and Development Au- thority, the Reservoir Characterization Group, may reflect the reactivation of inherited Eocambrian basement New York State Museum, the Ohio State Geo- structures, including the Rome trough and northwest-striking logical Survey, the Pennsylvania Geological Sur- cross-structural discontinuities, induced by Acadian plate con- vey, and Appalachian Fracture Systems sup- vergence. Episodes of block displacement locally warped the ported various aspects of this study. Randy Blood basin into northeast-southwest–trending regions of starved sedi- is acknowledged for the many field discussions mentation and/or erosion adjacent to depocenters in which re- related to the lithostratigraphy and sequence stratigraphy of the Middle and Upper Devonian gressive systems tract deposits were ponded. Block movement shale succession of the Appalachian Basin, including the Marcellus Formation. The AAPG Editor thanks the following reviewers for their work on this paper: Charles M. Boyer II, Ashton F. Embry, Karen S. Glaser, Ursula Copyright ©2011. The American Association of Petroleum Geologists. All rights reserved. Hammes, and Berry H. Tew Jr. Manuscript received September 4, 2009; provisional acceptance December 7, 2009; revised manuscript received March 22, 2010; final acceptance June 30, 2010. DOI:10.1306/06301009150 AAPG Bulletin, v. 95, no. 1 (January 2011), pp. 61–103 61 appears to have initiated in late Early Devonian Results reported on in this article are based on time, resulting first in thinning and local erosion of our analysis of more than 900 wireline logs from the Oriskany sandstone in northwest Pennsylvania. the Appalachian Basin of Pennsylvania, New York, This study, in addition to providing the basis for a northern West Virginia, eastern Ohio, and western predictive sequence-stratigraphic model that can Maryland (Figure 2). We focus on the Appalachian be used to further Marcellus exploration, tells of a Plateau region of the basin for three reasons: its foreland basin more tectonically complex than ac- greater density of available wireline logs, fewer counted for by simple flexural models. structural complications, and greater economic via- bility. Specific points addressedinthisstudyinclude (1) the distribution and thickness trends of the two black shale members of the Marcellus Formation; INTRODUCTION (2) the distribution and thickness of the intervening limestone, an interval that could be critical to stim- The much studied Hamilton Group of the Appala- ulation and production considerations; and (3) the chian Basin is an eastward and southeastward thick- stratigraphy and distribution of the organic-rich ening wedge of marine and nonmarine shale, silt- Levanna Shale Member of the Skaneateles Forma- stone, and sandstone (Cooper, 1933, 1934; Rickard, tion, a unit that has been confused with the Mar- 1989). To the west of the Hudson Valley, the Ham- cellus Formation. ilton succession is defined by an increasing abun- As important as the previous points are, how- dance of fossiliferous black and gray marine shale ever, the more significant contribution of this ar- interbedded with several thin laterally extensive ticle is a sequence-stratigraphic framework of the limestones (Cooper, 1930, 1933; de Witt et al., Marcellus Formation as deduced from publicly 1993). Hamilton Group deposits, part of the Cats- available wireline logs. Partington et al. (1993) and kill delta succession, accumulated in an elongate Emery and Myers (1996), among others, have foreland basin that formed in response to the Aca- demonstrated the use of some of the more com- dian oblique collision of the Avalonia microplate and mon wireline log suites to the interpretation of Laurentia (Figure 1; Ettensohn, 1985, 1987; Faill, sedimentary successions in terms of such sequence- 1985; Ferrill and Thomas, 1988; Rast and Skehan, stratigraphic elements as sequence boundaries, sys- 1993). Throughout much of the basin, the Middle tems tracts, condensed sections, and maximum Devonian Marcellus Formation (Hall, 1839), the flooding surfaces. Such an approach serves as a basal unit of the Hamilton Group, comprises two means by which basin fill can be organized into black shale intervals separated by a sequence of unconformity (or equivalent conformable surface) limestone, shale, and lesser sandstone of variable bounded packages of strata that provide a frame- thickness (Clarke, 1903; Cate, 1963; de Witt et al., work for predictive reservoir assessment and cor- 1993). Recent advances in well stimulation of, and relation into regions of minimal or poor data con- production from, Devonian–Mississippian black trol. Thickness trends of lithostratigraphic units and shale gas deposits of the eastern and southern the sequence stratigraphy of the Marcellus Forma- United States, including the Barnett, Fayetteville, tion reveal a basin that was more tectonically active and Woodford shales, have yielded similarly prom- than heretofore realized. Reactivated extensional ising results in the Marcellus Formation (Engelder basement structures, including Eocambrian faults et al., 2009). Continued successful exploration and associated with the Rome trough, and northwest- exploitation of the Marcellus necessitates an en- striking wrench faults (i.e., cross-strike structural hanced understanding of its stratigraphy, including discontinuities of Wheeler, 1980), appear to have thickness trends and compositional attributes of controlled sedimentation patterns of at least the the component units, throughout the core region upper Lower through lower Middle Devonian suc- of Marcellus production beneath the Appalachian cession, including the Marcellus Formation, in west- Plateau. ern New York and northwest Pennsylvania. 62 Stratigraphy of the Middle Devonian Marcellus Formation, Appalachian Basin Figure 1. (A) General tectonic reconstruction of the Appalachian orogenic belt during the Acadian orogeny showing approximate locations of synorogenic deposits. Modified from Ettensohn (1992) and Ferrill and Thomas (1988). (B) Diagram illustrating the inferred relationship among thrust loading, foreland basin subsidence, black shale sedimentation, and forebulge development. Modified from Ettensohn, 1994. Lash and Engelder 63 Figure 2. Base map of the core region of the Marcellus Formation basin in New York, Pennsylvania, eastern Ohio, western Maryland, and northern West Virginia. Symbols indicate the locations of wireline logs that were used in this study; numbered and lettered wells and cross-sections refer to text figure numbers. WC = Wayne County, Pennsylvania; SUC = Susquehanna County, Pennsylvania; WYC = Wyoming County, Pennsylvania; WAC = Washington County, Pennsylvania; GC = Greene County, Pennsylvania; SC = Sullivan County, New York; CC = Cayuga County, New York; BC = Broome County, New York. Figure 3. Comparison of the Marcellus Formation stratigraphy used in this study with the recently revised Marcellus stratigraphic nomenclature of Ver Straeten